The purpose of this four year project entitled Structural and social contexts of substance use, violence and HIV risk among adolescent gangs is to explore the relationship between differences in gang structure (size and complexity, initiation rites, rites of passage, gender composition, gender roles, and rules concerning substance use) of African American and Latino Milwaukee gangs, gang members' social context (including substance use, drug selling, social networks, and the context in which drugs are consumed and risky sex occurs), and environmental factors on the sexual risk behaviors of gang members. Specific aims include: 1. To compare gang structure, including differences in gender composition, size and complexity, gang initiation, and norms around drug selling and use among Latino and African American gangs in Milwaukee. 2. To identify differences in sexual risk behaviors among male and female members of different Latino and African American Milwaukee gangs. 3. To examine the impact of gang structure and environmental factors on gang members' risk behaviors and daily activities including involvement in substance use and illegal activities. The project will use qualitative and quantitative research methods. In the first phase, we will conduct in-depth interviews with 64 gang members. Gang members will be purposefully sampled to include male and female members of four different Latino and African American gangs. Gangs selected will include smaller, neighborhood based gangs, and larger corporate gangs. We will use the qualitative data to develop and pilot a quantitative survey measuring gang structure and members' daily activities including drug use, drug selling, the social context and physical setting in which sexual risk behaviors, drug and alcohol use occur. In the second phase of the project, we will administer the ACASI survey with 400 gang members, including members of gangs that were not part of the in-depth interviews to determine how gang structure, gang social context and environment influence sexual risk. In the final phase of the research, we will conduct a series of focus groups to help identify components of a multilevel prevention intervention, community resources that can be used to implement the intervention, and ways of tailoring interventions to appeal and meet the different needs of male and female gang members, and members of different ethnicities. We will have a Community Advisory Board, made up of community stakeholders and gang members, and a Scientific Advisor to advise us in all phases of the project.